1. Field of the Invention
The present invention generally relates to symbol capture devices, and more particularly, relates to a symbol capture device or other symbol capture device with guiding light beams for ascertaining the focal length and field of view at that focal length of an image capture device.
2. Description of the Related Art
Symbol capture devices used for reading symbols having data identifying characteristics such as barcodes are known. Typically, a symbol capture device has guiding light beams for suitable positioning including the positioning of focal length and field of view. That is to say, the symbol capture device needs to be positioned relative to the symbol located at a distance at an optimal position. Known methods to determine the optimum position include using laser light sources or light emitting diodes (LED). It is important to position the device correctly, because it operates as a CCD camera or the like, and the clarity of the image and effectiveness of reading is decreased if the position is incorrect.
FIG. 1 shows three prior art LED projection schemes on to a surface for use in positioning the surface to be read relative to the device. The drawbacks of prior art LED schemes are that the projections do not provide a clear field of view, and there is no indication of the focal plane at which the surface to be read should be positioned.
FIG. 2 is an alternative prior art arrangement using lasers. The laser provides the same visual display to a user regardless of distance between the device and the surface of the image. While it clearly shows the field of view, the cost is relatively high. Additionally, it is difficult to ascertain the focal length. It is desirable to have a system wherein the user can easily determine the proper focal length as well as the field of view of the image capture device at that focal length. The solution should have minimal cost.